Abstract: The single free face cutting blasting in roadway excavation is the key. In order to explore the calculation method
of delay time of straight-hole cutting blasting,a three-dimensional physical model of rock fragment throwing was established
based on the field blasting parameters and the formation process of blasting cavity. Then,based on the analysis of the dynamic
resistance of the throwing,based on the one-dimensional kinematics and gas-solid two-phase flow theory,the relationship between
the different positions of the rock fragments in the groove cavity and the initial velocity of the throwing,the formation time
of the groove cavity,and the delay time are derived. Finally,the influence of different delay time on blasting effect is analyzed
by SPH-FEM coupling numerical simulation and similar model test designed on the background of engineering site. The research
shows that after the blasting of the cut hole,the initial velocity of the rock fragment is generated under the expansion
pressure of the detonation gas,which determines the time for the rock fragment to be thrown into the cavity. The velocity of rock
fragments at different positions in the cavity can be calculated by the expansion time of explosive gas,and the closer to the face
of the tunnel,the greater the initial throwing velocity of rock fragments. The setting of delay time is closely related to the formation
time of the cavity. The theoretical calculation results show that the optimal delay time between the cut holes per meter is 15
~28 ms. The results of numerical analysis and similar model test show that the optimal delay time between the cut holes per
meter in the engineering site is 15~22 ms. The research results provide a certain reference for the selection of delay time of
straight cut blasting.